United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 94-50: Failure of General Electric Contactors to Pull in at the Required Voltage

UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.  20555

July 14, 1994


NRC INFORMATION NOTICE 94-50:  FAILURE OF GENERAL ELECTRIC CONTACTORS
                               TO PULL IN AT THE REQUIRED VOLTAGE


Addressees

All holders of operating licenses or construction permits for nuclear power
plants.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees that some full-voltage magnetic reversing
controllers manufactured by General Electric Electrical Distribution & Control
(GE ED&C) contained contactors with incorrect coils that would not close the
contacts under degraded voltage conditions.  It is expected that recipients
will review the information for applicability to their facilities and consider
actions, as appropriate, to avoid similar problems.  However, suggestions
contained in this information notice are not NRC requirements; therefore, no
specific action or written response is required.

Description of Circumstances

In November 1993, at Nine Mile Point Unit 2, as a result of testing certain
motor operated valves (MOVs) in the high pressure core spray system, plant
personnel found that the controllers for four of the MOV motors would not pull
in (contactors would not close) at 80 percent of rated voltage as specified in
the procurement documents.  In all, six CR209D type controllers in the same
Division III motor control center were affected.  The licensee determined that
this condition could have prevented the system from performing its safety
function and reported the circumstances to the NRC in accordance with Part 21
of Title 10 of the Code of Federal Regulations (10 CFR Part 21).  These
controllers had a National Electrical Manufacturers Association (NEMA) rating.

Discussion

Niagara Mohawk Power Company, the licensee for Nine Mile Point, purchased the
high pressure core spray system and the associated electrical components from
GE Nuclear Energy (GE NE).  This included the motor control center which was
manufactured for GE NE by GE ED&C.  The requirement in the GE NE purchase
specification, that NEMA size 1, 2 and 3 controllers in the switchgear should
be capable of closing at 80 percent of rated voltage, was a plant interface
requirement.

A test procedure performed during plant startup showed that the minimum
voltage at which the contactors in these controllers would pull in was greater

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94-50                                                              July 14,
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than 80 percent of rated voltage, but the test procedure did not contain this
acceptance criterion and no corrective action was taken.  Consequently, if a
design-basis accident occurred and system voltage was degraded, these
contactors may not have actuated and closed the contacts to operate the
affected valves.  In this circumstance, the current drawn by the coils remains
high and may cause the control power fuse(s) to blow as happened during some
of the testing at Nine Mile Point Unit 2.

GE NE informed the NRC that the contactors for the six controllers at Nine
Mile Point Unit 2 had been assembled at the GE ED&C factory with standard
coils designed to close the contacts at 85 percent of rated voltage.  The part
number for the standard coil is "15D222G22" which is the part number the
licensee reported stamped on the contactor coils.  GE NE indicated that a
special coil with a 75-percent pull-in rating would have been needed to meet
the 80-percent pull-in rating specified in the procurement documents for the
affected NEMA size 2 contactors and that the part number for this special coil
would have been "55-523759G022."  However, this part number is not (and was
not) listed in the applicable GE ED&C commercial catalog (currently Catalog
No. GEP-1260).

In the GE ED&C catalog, a two-digit suffix at the end of the part number for
NEMA-rated contactors, starters, or controllers, specifies the coil voltage
rating.  At the time that the controllers for the affected MOVs were ordered,
the suffix "22" indicated a standard coil for a voltage and frequency rating
of 115-120 Vac/60 hertz or 110 Vac/50 hertz that would pull in at 85 percent
of rated voltage.  However, the suffix "22" is no longer used.  Currently,
this dual voltage and frequency rating is specified by the suffix "02" and
still refers to a standard coil designed to pull in at 85 percent of rated
voltage.  The suffix "02" was formerly used to specify a nominal 120 Vac/60
hertz coil.

GE NE stated that, if a coil rated to pull in at 75 percent of rated voltage
is required, that requirement and the special coil part number or the coil
suffix to the catalog number of the contactor, starter, or controller being
procured from GE NE (if available) should be included in the procurement
documents sent to GE NE.  GE NE also stated that GE ED&C does not normally
provide this information nor normally supply coils rated to pull in at
75 percent of rated voltage to its commercial customers.  However, licensees
are responsible for ensuring that procurement documents specify or reference
applicable requirements and that purchased material and components conform to
the requirements in the procurement documents.

The six controllers whose contactors would not close under the degraded
voltage conditions required in the purchase specification had been installed
at Nine Mile Point Unit 2 during initial plant construction.  Because test
procedures failed to verify that the contactors would close at the minimum
expected voltage for design basis conditions, this condition remained
uncorrected for several years.  Testing these or other electromagnet-operated
devices at minimum expected voltage (and under certain circumstances, maximum
expected temperature) should detect incorrect or inadequately wound coils and
also coils that are degraded. GE ED&C stated that all of their contactors with
standard coils are tested at 85 percent of rated voltage.  However, that.
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of 3


testing may not verify individual plant requirements.  Further, not all
manufacturers of electromagnet-operated devices test all production units.
Some manufacturers may test on a random sample basis and only at nominal or
rated voltage.  The licensee for Nine Mile Point Unit 2 has replaced the
controllers in the four affected MOVs with Gould controllers designed to pull
in at 75 percent of rated voltage.

The condition described above may affect other plants.  In NRC Generic Letter
89-10, "Safety-Related Motor-Operated Valve Testing and Surveillance," the NRC
requested licensees and holders of construction permits  to conduct reviews
and verifications of the design and performance of certain MOVs and to take
appropriate corrective actions.  As part of their response to GL 89-10, some
licensees have found that the degraded voltage condition for certain MOVs is
less than 80 percent of rated voltage, which is lower than the capability of
the GE standard 85 percent coil.  Contactors that are not designed to close at
the appropriate degraded voltage and tested to verify that capability may be
unable to operate those MOVs if degraded voltage conditions occur.

This information notice requires no specific action or written response.  If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.

/s/'d by BKGrimes


                        Brian K. Grimes, Director
                        Division of Operating Reactor Support
                        Office of Nuclear Reactor Regulation


Technical contacts:  Kamalakar Naidu, NRR
               (301) 504-2980

                     Stephen Alexander, NRR
               (301) 504-2995

           Leonard Cheung, RI
               (610) 337-5296


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